Since a wireless communication unit of a portable terminal type essentially requires battery operation in general, suppressing the power consumption of the entire terminal hitherto has been a technical issue.
FIG. 8 is a block diagram to show the configuration of a wireless communication unit of a related art example; the operation of which for suppressing power consumption will be described below.
A wireless communication unit is made up of: antenna 501 for performing transmission/reception of a high-frequency signal to and from another wireless communication unit; transmitting/receiving circuit 511 for performing analog processing of a high-frequency signal; baseband. processing part 507 for performing modulation/demodulation of a high-frequency signal to control the wireless communication unit; and application processing part 508 for performing audio processing etc.
Transmitting/receiving circuit 511 is made up of: transmitting part 502 for transmitting a high-frequency signal; receiving part 503 for receiving a high-frequency signal; antenna change-over switch 504 for switching between transmission by transmitting part 502 and reception by receiving part 503; and timer 505 for intermittently activating necessary components.
Baseband processing part 507 is made up of: modulation/demodulation part 509 for performing baseband modulation/demodulation of a signal; own station determination part 506 which determines whether or not a received signal is addressed to own unit and, when determined that it is addressed to the own unit, supplies power to respective components to activate them; and control part 510 for controlling each part and the flow of the signal in each part of the wireless communication unit.
Application processing part 508 is made up of: audio processing part 518 for processing voices; and application part 528 for processing data, information, and others.
Conventionally, it has been necessary for a wireless communication unit that transmitting/receiving circuit 511 be constantly operated to share the network information with another wireless communication unit, which is the communication counterpart, so as to be ready to be connected to a communications line whenever communication is needed.
On the other hand, various proposals for suppressing the power consumption of a wireless communication unit have been made.
A first method of suppressing power consumption is the method of providing an arrangement in which power is not supplied unless otherwise required, to the components that are not directly related to wireless communication, from among the components of application processing part 508, and this method is being commonly used.
A more advanced method of suppressing power consumption is the method of putting a wireless communication unit into a reception standby state in such a way that only receiving part 503 of transmitting/receiving circuit 511, baseband processing part 507, and own station determination part 506 are operated and such that the other components of the wireless communication unit are powered off.
Further, a PHS (Personal Handyphone System) has been proposed in which timer 505 is used in the mobile station to turn off the power supply of the transmitting circuit and to intermittently operate the receiving circuit during standby of the mobile station so that the current consumption during standby of the mobile station is reduced, thereby increasing battery life (see Patent document 1).
Further, in a wireless communication unit for 1-to-1 communication such as a simple wireless interphone, a specified low-power wireless communication equipment is proposed in which a diode detector circuit, a low-frequency amplifier circuit and a logic circuit are provided in the subsequent stage to a high-frequency amplifier part to enable the determination of the presence or absence of a received signal so that the switch is closed, only upon determination of the presence of a received signal, to supply power to each part making up the specified low-power wireless communication equipment, thereby avoiding the wasting of power (see Patent document 2).
Further, there has been also proposed a communication apparatus in which a control part and a communication part, which consumes relatively low power, are provided, and the control part activates the low power consuming communication part, putting it into a standby state at a low power consumption and, when communication is started at the low power consuming communication part and a communication line is established, activates a communication part for high data rate communication to perform communications (see Patent Document 3).
Patent document 1: Japanese Patent Laid-Open No. 08-116301.
Patent document 2: Japanese Patent Laid-Open No. 06-120853.
Patent document 3: Japanese Patent Laid-Open No. 2003-124862.
However, for a mobile wireless/PHS whose sensitivity cannot be reduced in terms of maintaining its communication quality, receiving part 503 requires a high-sensitivity and complex configuration typified by a superheterodyne scheme.
However, because the superheterodyne scheme, however, requires heavily equipped circuits having a complicated configuration, such as a high-frequency amplification circuit and a medium-frequency amplification circuit, in addition to a local oscillator (typically including a complicated circuit of a phase-locked loop configuration) and a mixer circuit for stably performing frequency conversion, it is not easy to reduce power consumption of the circuit itself.
Therefore, a problem exists in that there is no way to control the amount of power to be consumed except through an intermittent operation by means of timer 505.
However, as it is well known, the battery life in a mobile radio system such as PHS tends to be merely 300 to 400 hours at the longest.
In an exemplary disclosure of Patent document 2, although the power during standby is suppressed by providing a circuit for detecting the presence or absence of a carrier wave, and the circuit is simplified by making it dedicated a carrier wave, there is a problem in that this method will not be effective unless 1-to-1 communication with a fixed party is assumed.
Because a method which detects the presence or absence of a signal of a carrier wave, is likely to be responsive to a carrier wave signal from another wireless system not anticipated, this will result in malfunction of the communication unit that is being used.
Thus, a problem exists in that the suppression of power consumption of a wireless communication unit is only intended for wireless systems which are currently being used as 1-to-1 communication or an equivalent thereof.
Further, since the communication apparatus disclosed in Patent document 3 utilizes different kinds of communication media such as infrared radiation and extremely low-power radio waves, a problem exists in that a dedicated transmitting part is required.
Thus, it is an object of the present invention to provide a wireless communication unit which is operated by a battery and offers long battery life, and a wireless network which utilizes the wireless communication unit.